From the practical point of view, even in our days probably the attainment of CCyR or 1 % BCR-ABL can still be considered the most significant response to target, as this goal has been demonstrated to be associated to the highest probability of long-term survival for CML patients who better benefit from the TKI therapy are those who achieve and maintain CCyR for at least 2 years, as in these cases the OS is similar to that of a control population without leukemia [7•, 8, 9, 18]. The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.